Vehicle passenger detection system

ABSTRACT

A vehicle passenger detection apparatus includes a load detecting part and a seat condition determining part. The seat condition determining part includes a vibration threshold value setting section, a vibration determining section and a seat determining section. The vibration threshold value setting section sets a vibration threshold value based on the load detection signal such that the vibration threshold value is higher when a fluctuation amount of the load detection signal is small than when the fluctuation amount of the load detection signal is large. The seat determining section executes a seating determination based on the load detection signal when the vibration determining section determines that the vehicle vibration is not occurring based on the load detection signal and the vibration threshold value, and to defer execution of the seating determination to maintain a previous seating determination result when the vibration determining section determines that the vehicle vibration is occurring.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to Japanese Patent Application No.2011-108331 filed on May 13, 2011. The entire disclosure of JapanesePatent Application No. 2011-108331 is hereby incorporated herein byreference.

BACKGROUND

1. Technical Field

The present invention relates to a vehicle passenger detection apparatusthat is installed in an automobile or other vehicle and used todetermine whether or not to activate an air bag device provided in thevehicle.

2. Related Art

Air bag systems that can protect a passenger seated in a seat have beenprovided in automobiles and other vehicles for some time. Such an airbag system has a vehicle passenger detection apparatus that determinesif a passenger is seated in a seat or not and if a seated passenger isan adult or a child. The vehicle passenger detection apparatus has aload sensor installed on a set periphery and a seat conditiondetermining part that executes a seating determination based on adetection signal from a load sensor (e.g., see Japanese Patent Number4339368). However, when the vehicle is moving or in another state inwhich a vehicle vibration occurs, a detection signal from the loadsensor varies severely and there is a possibility a seatingdetermination will be incorrect. Therefore, a vehicle passengerdetection apparatus has been conceived that defers a seatingdetermination at a previous determination result when the vehicle ismoving or in another state in which vehicle vibrations are comparativelylarge and executes a seating determination when the vehicle is stoppedor in another state in which vehicle vibrations are comparatively small.

SUMMARY

When a seating determination is executed or deferred depending on thesize of a vehicle vibration, there are situations in which the precisionof the seating determination may decline. For example, if a passengerboards the vehicle while it is stopped and does not sit fully and stablyin the seat until after the vehicle is moving, then the precision of theseating determination will decline because the passenger did not have astable posture when the vehicle was stopped and vehicle vibrations werecomparatively small. Meanwhile, when the vehicle is moving and thepassenger is seated in a stable fashion, the seating determination isdeferred because the vehicle vibrations are comparatively large. Thus,in some cases, it is desirable to execute a seating determination whilea vehicle is moving and vehicle vibrations are comparatively large.

Even when the vehicle is stopped and vehicle vibrations arecomparatively small, if a seating determination is executed according tothe size of vehicle vibrations, then there is a possibility that avehicle vibration caused by a condition of a passenger will be detectedand cause the seating determination to be deferred.

Therefore, an object of the present invention is to provide a vehiclepassenger detection apparatus that can reduce deferments of a seatingdetermination and increase opportunities for executing the seatingdetermination when a size of a vehicle vibration is used to decidewhether to execute or to defer a seating determination.

In order to achieve the aforementioned object, a vehicle passengerdetection apparatus according to one aspect of the present inventionincludes a load detecting part and a seat condition determining part.The load detecting part is installed in the vicinity of a seat of avehicle to detect a load acting on the seat. The seat conditiondetermining part is configured to determine a condition of the seatbased on a load detection signal from the load detecting part. The seatcondition determining part includes a vibration threshold value settingsection, a vibration determining section and a seat determining section.The vibration threshold value setting section is configured to set avibration threshold value based on the load detection signal such thatthe vibration threshold value is higher when a fluctuation amount of theload detection signal is small than when the fluctuation amount of theload detection signal is large. The vibration determining section isconfigured to determine if the vehicle vibration is occurring based onthe load detection signal and the vibration threshold value. The seatdetermining section is configured to execute a seating determinationbased on the load detection signal when the vibration determiningsection determines that the vehicle vibration is not occurring, and todefer execution of the seating determination to maintain a previousseating determination result when the vibration determining sectiondetermines that the vehicle vibration is occurring.

With this aspect of the present invention, the vibration threshold valuesetting section sets the vibration threshold value to a higher valuewhen a fluctuation amount of the load detection signal is small thanwhen the fluctuation amount of the load detection signal is large. Thus,setting the vibration threshold value higher serves to decrease thelikelihood that the vibration determining section (which determineswhether or not a vehicle vibration is occurring) will determine that avehicle vibration has occurred. In other words, when the fluctuationamount of the load detection signal is small, the vibration determiningsection is more likely to determine that the vehicle vibration is notoccurring than when the fluctuation amount of the load detection signalis large.

As a result, for example, when a passenger's posture causes a vibrationto occur while the vehicle is moving or stopped, if the fluctuationamount of the load detection signal is small and the load detectionsignal is stable, then the vibration threshold value is set high and theapparatus will be more likely to determine that a vehicle vibration isnot occurring. If it is determined that a vehicle vibration is notoccurring, then the seat determining section executes a seatingdetermination and the opportunities for executing a determination can beincreased.

As a result, deferments of the seating determination can be decreasedand opportunities for executing the seating determination can beincreased when the size of a vehicle vibration is used to decide whetherto execute or defer the seating determination.

BRIEF DESCRIPTION OF THE DRAWINGS

Referring now to the attached drawings which form a part of thisoriginal disclosure:

FIG. 1 is schematic plan view of a vehicle equipped with a vehiclepassenger detection apparatus according to an embodiment.

FIG. 2 is a block diagram of an air bag system having a vehiclepassenger detection apparatus according to the embodiment.

FIG. 3A is a plan view, FIG. 3B is a side view, and FIG. 3C is a frontalview illustrating an installed state of a load detecting part of avehicle passenger detection apparatus according to the embodiment withrespect to a seat.

FIG. 4 is a graph showing how a load detection signal differs when thenumber of load detecting part installed is different.

FIG. 5 is a flowchart of a passenger detection process executed by thevehicle passenger detection apparatus according to the embodiment.

FIG. 6 is a time chart showing characteristic plots of a vibrationchange amount, a load change amount, a detected load (four-pointsensor), and a detected load (two-point sensor) obtained when a vehicleis moving with an adult passenger.

FIG. 7 is a time chart showing characteristic plots of a vibrationchange amount, a load change amount, a detected load (four-pointsensor), and a detected load (two-point sensor) obtained when a vehicleis stopped with an adult passenger.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

Selected embodiments will now be explained with reference to thedrawings. It will be apparent to those skilled in the art from thisdisclosure that the following descriptions of the embodiments areprovided for illustration only and not for the purpose of limiting theinvention as defined by the appended claims and their equivalents.

FIG. 1 is schematic plan view of a vehicle equipped with a vehiclepassenger detection apparatus according to one embodiment. FIG. 2 is ablock diagram of an air bag system having a vehicle passenger detectionapparatus according to the embodiment.

As shown in FIG. 1, a plurality of seats 2 for passengers to sit on andan air bag system 3 that can protect a passenger seated on a seat 2 areinstalled in a vehicle 1 (automobile or the like). As shown in FIG. 2,the air bag system 3 comprises an air bag 4, a passenger conditionindicator lamp 5, a warning lamp 6, an air bag ECU 7, and a vehiclepassenger detection apparatus 10.

The air bag 4 is stored frontward of one of the seats 2 (a passengerseat 2 a in this embodiment) inside an instrument panel 8 arranged in afrontward portion of a vehicle cabin. The air bag 4 serves to protect apassenger during a vehicle collision by deploying and exhibiting animpact absorbing function. A deployment size of the air bag 4 can bevaried to at least two different sizes in accordance with a deploymentsignal from the air bag ECU 7.

The passenger condition indicator lamp 5 is installed in the instrumentpanel 8 arranged in a frontward portion of the vehicle cabin andindicates a passenger condition detection result for the passenger seat2 a in accordance with an indication signal from the air bag ECU 7.Examples of passenger conditions include no passenger, seated adult, andchild seat.

The warning lamp 6 is installed in the instrument panel 8 arranged in afrontward portion of the vehicle cabin and illuminates as a warningindication in response to a failure signal issued from the air bag ECU 7when a failure has been detected in the air bag system.

The air bag ECU 7 has an internal CPU 7 a and serves to execute adeployment determination with respect to the air bag 4 based on seatinformation obtained from the vehicle passenger detection apparatus 10and to issue a deployment signal to the air bag 4. The deploymentdetermination includes such determination results as not to deploy theair bag 4 when a passenger is not sitting in the passenger seat 2 a, todeploy the air bag 4 when an adult is sitting in the passenger seat 2 a,and not to deploy the air bag 4 when a child seat is being used to seata child in the passenger seat 2 a. The air bag ECU 7 also issues anindication signal to the passenger condition indicator lamp 5 based onseat information obtained from the vehicle passenger detection apparatus10 and issues a failure signal to the warning lamp 6 when a failure isdetected in the air bag system.

The vehicle passenger detection apparatus 10 comprises a plurality ofload sensors (load detecting part) 11 and a passenger detection ECU(seat condition determining part) 12 and serves to determine a state ofthe seat 2 (the passenger seat 2 a in this explanation) and send seatinformation to the air bag ECU 7.

The load sensors 11 are attached to a periphery of the passenger seat 2a (one of the seats 2) and detect loads acting on the passenger seat 2a. As shown in FIGS. 3A to 3C, each of the seats 2 (including thepassenger seat 2 a) is attached to a vehicle body 21 through aleft-right pair of slide rails 22 and 23 such that the seat can slide(position can be adjusted) in a longitudinal direction 24 of the vehiclealong the slide rails 22 and 23. The seat 2 is supported at a total offour locations with respect to the pair of slide rails 22 and 23, i.e.,at front and rear support points 24 a to 24 d on each of the left andright sides.

Thus, if the seat 2 is supported with respect to the vehicle body 21 ata plurality of support points 24 a to 24 d, then a load sensor 11 isinstalled with respect to at least one of the support points 24 a to 24d and not installed with respect to at least one of the support points24 a to 24 d. In other words, at least one of the support points 24 a to24 d does not have a load sensor 11 installed, thus establishing a loaddetecting part omitted section.

In the illustrated embodiment, a total of two load sensors 11 areprovided, i.e., a load sensor 11 a is installed with respect to thefront support point 24 a and a load sensor 11 b is installed withrespect the rear support point 24 b of the slide rail 22, which is theslide rail located more toward an inward side of the vehicle body 21.

Thus, the two support points 24 c and 24 d where the seat is supportedon the slide rail 23 located more toward an outward side the vehiclebody 21 are load detecting part omitted sections.

FIG. 4 is a graph showing how a load detection signal differs when thenumber of load detecting part installed is different. In FIG. 4, thecurve e illustrates a total sum of the load detection signals in a caseaccording to the illustrated embodiment in which two load sensors 11 areprovided such that one is located at the frontward support point 24 aand one is located at the rearward support point 24 b, and the curve fillustrates a total sum of the load detection signals for a case inwhich a load sensor 11 is provided at each of all four support points 24a to 24 d.

The magnitude of the total load detection signal for a case in whichload sensors 11 are provided in two locations is approximately one-halfthe size of the magnitude of the total load detection signal for a casein which load sensors 11 are provided at all four of the support points24 a to 24 d when the vehicle is traveling on a straight path, asindicated by the curve e and the curve f. When the vehicle travelsthrough a curve, the magnitude of the total load detection signaldecreases greatly in comparison with traveling on a straight path. Thisphenomenon is believed to be caused by a centrifugal force acting on theside opposite the side where the load sensors 11 are provided andcausing the detected load to decrease.

Conversely, when load sensors 11 are installed at all of the supportpoints 24 a to 24 d, as indicated by the curve f, the magnitude of thetotal load detection signal is stable regardless of whether the vehicletravels on a straight path or through a curve. This stability isbelieved to occur because a balance is achieved when the outputs of theload sensors 11 are summed together even if a centrifugal force exists.

It is also acceptable to provide load sensors 11 arranged at acombination of two support points among the support points 24 a to 24 dother than the combination already explained, i.e., at the front andrear support points 24 c and 24 d of the slide rail 23 located towardthe outward side of the vehicle body 21, at the front support points 24a and 24 c, at the rear support points 24 b and 24 d, or at thediagonally positioned support points 24 a and 24 d or 24 c and 24 b. Itis also acceptable to provide load sensors 11 in three locations andleave only one of front and rear support points 24 a to 24 d without.Furthermore, it is acceptable to provide a load sensor 11 at only one ofthe front and rear support points 24 a to 24 d. However, since, aspreviously explained, the magnitude and stability of the total loaddetection signal degrade as the number of load sensors 11 installed isdecreased, it is preferable to install load sensors 11 in two or threelocations instead of one.

The passenger detection ECU 12 has a CPU 12 a and serves to determine asitting condition of the seat 2 based on load detection signals from theload sensors 11. The CPU 12 a has a signal converting section 13, avibration waveform removing section 14, a load change amountdetermination logic (vibration threshold value setting section) 15, avibration change amount determination logic (vibration determiningsection) 16, and a seat determining section 17.

The signal converting section 13 converts the analog load detectionsignals outputted from the load sensors 11 a and 11 b into digitalsignals. A separate signal converting section 13 is provided withrespect to each of the load sensors 11 a and 11 b installed on thepassenger seat 2 a and indicated as “A/D” in FIG. 2.

The vibration waveform removing section 14 removes a vibration waveformindicating that a vibration is occurring from a load detection signalconverted to digital by the signal converting section 13 and generates avibration waveform removed signal. The “vibration waveform” is, forexample, a high frequency vibration component (travel vibration)oriented in a vertical direction. The vibration waveform removingsection 14 uses a low pass filter that can remove such vibrationwaveforms as, for example, a high frequency vibration component. Aseparate vibration waveform removing section 14 is provided with respectto each of the signal converting sections 13 and indicated as “LPF” inFIG. 2.

The load change amount determination logic 15 sets a vibration thresholdvalue based on the vibration waveform removed signal, i.e., the loaddetection signal resulting after the vibration waveform removing section14 has removed the vibration waveform from the load detection signal.The threshold value is a value that will serve as a reference whendetermining if a vehicle vibration is occurring. The load change amountdetermination logic 15 sets the vibration threshold value to a highervalue when the fluctuation amount of the vibration waveform removedsignal is small than when the fluctuation amount of the vibrationwaveform removed signal is large. More particularly, in the illustratedembodiment, when a state in which the fluctuation amount of thevibration waveform removed signal is small has continued for aprescribed amount of time, the vibration threshold value is set to ahigher value than when the fluctuation amount of the vibration waveformremoved signal is large.

How the vibration threshold value is set will now be explained. A sum ofthe vibration waveform removed signals is calculated and an absolutevalue of a fluctuation amount of this sum is calculated as a loadfluctuation amount. The load fluctuation amount is then compared to aweight threshold value already prepared in the load change amountdetermination logic 15. If a state in which the load fluctuation amountis equal to or smaller than the weight threshold value continues for aprescribed amount of time, then the load acting on the passenger seat 2a is stable, i.e., the outputted weight information is stable, and thevibration threshold value is set to a higher value. Meanwhile, if theload fluctuation amount exceeds the weight threshold value, then theload acting on the passenger seat 2 a is unstable, i.e., the outputtedweight information is unstable, and the vibration threshold value is setto a low value.

The vibration change amount determination logic 16 determines if avehicle vibration is occurring based on the load detection signaldigitized by the signal converting section 13 and the vibrationthreshold value set by the load change amount determination logic 15.The “load detection signal digitized by the signal converting section13” is the digital load detection signal as it exists before thevibration waveform is removed by the vibration waveform removing section14 and, thus, still includes the vibration waveform. How a determinationis made as to whether a vehicle vibration is occurring will now beexplained. An absolute value of a fluctuation amount of each of the loaddetection signals from the load sensors 11 a and 11 b is calculated. Atotal sum of the absolute values of the fluctuation amounts iscalculated as a vibration change amount and the vibration change amountis compared to the vibration threshold value set by the load changeamount determination logic 15. If the vibration change amount is equalto or larger than the vibration threshold value, then it is determinedthat a vehicle vibration is occurring. If the vibration change amount issmaller than the vibration threshold value, then it is determined that avehicle vibration is not occurring.

The seat determining section 17 executes a seating determination basedon a load detection signal or defers the seating determination inaccordance with the size of a vehicle vibration. The seat determiningsection 17 has a passenger determination logic 17 a and a passengerdetermination logic 17 b.

The passenger determination logic 17 a executes a seating determinationbased on the vibration waveform removed signal, i.e., the load detectionsignal resulting after the vibration waveform removing section 14 hasremoved the vibration waveform from the load detection signal. The“seating determination” mentioned here means to execute a seatedpassenger determination to determine if a passenger is sitting on thepassenger seat 2 a and a body type determination to determine if apassenger sitting on the passenger seat 2 a has a large body type (e.g.,if a seated passenger is an adult or a child using a child seat). It isalso acceptable to execute one or the other of these determinations.More specifically, the seating determination involves finding a detectedload as a total sum of vibration waveform removed signals and comparingthe detected load to a first threshold value, a second threshold value,and a third threshold value already provided in the passengerdetermination logic 17 a. The logic then determines that an adult issitting if the detected load is equal to or larger than the firstthreshold value, that a child is sitting using a child seat if thedetected load is equal to or larger than the second threshold value butsmaller than the first threshold value, and that the seat is empty ifthe detected load is equal to or larger than the third threshold valuebut smaller than the second threshold value.

The passenger determination logic 17 b determines if the seatinformation should be updated based on a determination result from thevibration change amount determination logic 16 and sets the obtainedseat information to the air bag ECU 7. That is, if the vibration changeamount determination logic 16 has determined that a vehicle vibration isnot occurring, then the passenger determination logic 17 b treats theseating determination result from the passenger determination logic 17 aas new seat information and updates the seat information. Meanwhile, ifthe vibration change amount determination logic 16 has determined that avehicle vibration is occurring, then the passenger determination logic17 b does not treat the seating determination result from the passengerdetermination logic 17 a as new seat information and maintains the seatinformation from the previous control cycle.

In this way, the seat determining section 17 executes a seatingdetermination when it has determined that a vehicle vibration is notoccurring and maintains the seating determination result of the previouscycle by deferring execution of a seating determination when it hasdetermined that a vehicle vibration is occurring.

FIG. 5 is a flowchart of a passenger detection process executed by thevehicle passenger detection apparatus according to the illustratedembodiment. The steps of FIG. 5 will now be explained.

In step S1, the apparatus reads load detection signals (Sen1(t),Sen2(t)) constituting weight information from each of the load sensors11 a and 11 b installed on a seat (the passenger seat 2 a in thisexplanation) and proceeds to step S2 and step S5.

After reading the load detection signals in step S1, in step S2 theapparatus removes a vibration waveform constituting a high frequencyvibration component from each of the load detection signals and obtainsvibration waveform removed signals (LPF_Sen1(t), LPF_Sen2(t))corresponding to the load sensors 11 a and 11 b. The apparatus thenproceeds to step S3. The removal of the vibration waveform isaccomplished by executing a low pass filter process.

After removing the vibration waveform in step S2, in step S3 theapparatus calculates a detected load W by calculating a sum of thevibration waveform removed signals obtained by removing the vibrationwaveforms. The apparatus then proceeds to steps S4 and S6.

The detected load W is calculated using the equation (1) shown below.

W=LPF _(—) Sen1(t)+LPF _(—) Sen2(t)  (1)

After calculating the detected load W in step S3, in step S4 theapparatus executes a seating determination and proceeds to step S11.

This seating determination involves comparing the detected weight W to afirst threshold value TH/Lα1, a second threshold value TH/Lα2, and athird threshold value TH/Lα3 already provided in the passengerdetermination logic 17 a and finding a seating determination resultaccording to the equations (2) to (4) below.

W≧TH/Lα1=adult seated  (2)

Th/Lα1>W≧TH/Lα2=child seated in a child seat  (3)

TH/Lα2>W≧TH/Lα3=empty seat  (4)

After reading the load detection signals in step S1, in step S5 theapparatus finds an absolute value of a fluctuation amount (ΔSen1, ΔSen2)of each of the load detection signals and calculates a sum ΔSum of theabsolute values of the fluctuation amounts. The fluctuation amountscorrespond to vibration waveforms and the sum is a vibration changeamount. The apparatus then proceeds to step S11.

The absolute values (ΔSen1 and ΔSen2) of the fluctuation amounts of theload detection signals are calculated using the equations (5) and (6)show below, and the vibration change amount ΔSum equal to the sum of theabsolute values of the fluctuation amounts is calculated using theequation (7). The reason absolute values are used is to prevent thevibration waveforms detected by the load sensors 11 a and 11 b fromcancelling each other out and to emphasize the vibration waveform.

ΔSen1=abs(Sen1(t)−Sen1(t−1))  (5)

ΔSen2=abs(Sen2(t)−Sen2(t−1))  (6)

ΔSum={abs(Sen1(t)−Sen1(t−1))}+{abs(Sen2(t)−Sen2(t−1))}  (7)

After calculating the detected load W in step S3, in step S6 theapparatus calculates a load fluctuation amount ΔW by finding theabsolute value of a fluctuation amount of the detected load W andproceeds to step S7.

The absolute value (load fluctuation amount) ΔW of the detected weight Wis calculated using the equation (8) shown below.

ΔW=abs(W(t)−W(t−1))  (8)

After calculating the load fluctuation amount ΔW in step S6, in step S7the apparatus determines if the load fluctuation amount ΔW is equal toor smaller than a weight threshold value TH/Lβ already provided in theload change amount determination logic 15. If the determination resultis Yes (ΔW≦LH/Lβ), then a load fluctuation has not occurred, i.e., theweight information output is stable, and the apparatus proceeds to stepS8. If the determination result is No (ΔW>TH/Lβ), then a loadfluctuation has occurred, i.e., the weight information is unstable, andthe apparatus proceeds to step S10.

After determining that a load fluctuation has not occurred in step S7,in step S8 the apparatus determines if a prescribed amount of time(e.g., 3 seconds) has elapsed. If Yes (the prescribed amount of time haselapsed), then the weight information is stable and the apparatusproceeds to step S9. If No (the prescribed amount of time has notelapse), then a load fluctuation is occurring, i.e., the weightinformation is unstable, and the apparatus proceeds to step S10.

After determining that the weight information is stable in step S8, instep S9 the apparatus sets the vibration threshold value to a high value(TH/LαHigh) and proceeds to step S11.

After determining that the weight information is unstable in step S7 orstep S8, in step S10 the apparatus sets the vibration threshold value toa low value (TH/LαLow) and proceeds to step S11. What is considered ahigh value and a low value for the vibration threshold value isrelative. So long as the relationship TH/LαHigh>TH/LαLow is maintained,any values can be set as the threshold values.

After the seating determination has been executed in step S4, thevibration change amount ΔSum has been calculated in step S5, thevibration threshold value has been set (TH/LαHigh or TH/LαLow) in stepS9 or step S10, the apparatus proceeds to step S11 and determines if thevibration change amount ΔSum is equal to or larger than the vibrationthreshold value (TH/LαHigh or TH/LαLow). If Yes (ΔSum≧TH/LαHigh orTH/LαLow), then the apparatus proceeds to step S12. If No(ΔSum<TH/LαHigh or TH/LαLow), then the apparatus proceeds to step S13.

After determining that the vibration change amount ΔSum is equal to orlarger than the vibration threshold value (TH/LαHigh or TH/LαLow) instep S11, in step S12 the apparatus deems that a vehicle vibration isoccurring and maintains the seat information of the previous controlcycle without treating the seating determination result obtained in stepS4 as new seat information. Thus, the apparatus outputs the same seatinformation as in the previous cycle.

After determining that the vibration change amount ΔSum is smaller thanthe vibration threshold value (TH/LαHigh or TH/LαLow) in step S11, instep S13 the apparatus deems that a vehicle vibration is not occurringand updates the seat information by treating the seating determinationresult obtained in step S4 as new seat information. Thus, the apparatusoutputs the new seat information obtained in step S4.

The operation of the apparatus will now be explained.

FIG. 6 is a time chart showing characteristic plots of a vibrationchange amount, a load change amount, a detected load (four-pointsensor), and a detected load (two-point sensor) obtained when a vehicleis moving with an adult passenger. FIG. 7 is a time chart showingcharacteristic plots of a vibration change amount, a load change amount,a detected load (four-point sensor), and a detected load (two-pointsensor) obtained when a vehicle is stopped with an adult passenger.

First a passenger detection process according to a comparative exampleand disadvantages of the comparative example will be explained. Theoperation of a vehicle passenger detection apparatus according to theillustrated embodiment will then be explained in terms of passengerdetection operation when the vehicle is moving and passenger detectionoperation when the vehicle is stopped.

Passenger Detection Process According to Comparative Example andDisadvantages Thereof

In the passenger detection process according to the comparative example,the seating determination is deferred and the determination result fromthe previous cycle is maintained when a vehicle vibration iscomparatively large and the seating determination is executed when thevehicle vibration is comparatively small. Thus, a vibration thresholdvalue is set in advance with respect to a vibration change amountcalculated as the sum of absolute values of fluctuation amounts of aplurality of load detection signals. The vehicle vibration is determinedto be large if the vibration change amount is equal to or larger thanthe vibration threshold value, and the vehicle vibration is determinedto be small if the vibration change amount is smaller than the vibrationthreshold value. A situation in which the vibration threshold value isTH/LαLow will now be considered with reference to FIG. 6 and FIG. 7.

FIG. 6 illustrates the characteristic curves for a vehicle that ismoving while carrying an adult passenger (a 49-kg woman). During aperiod from a time t0 to a time t3, the vibration change amount is abovethe vibration threshold value TH/LαLow. Therefore, the seatingdetermination is deferred and the determination result from the previouscontrol cycle is maintained. During a period from the time t3 to a timet4, the vibration change amount intermittently falls below the vibrationthreshold value TH/LαLow. vibration change amount does not stay belowthe vibration threshold value TH/LαLow continuously. Then, after thetime t4, the vibration change amount completely exceeds the vibrationthreshold value TH/LαLow and the seating determination cannot beexecuted.

If the vibration change amount is comparatively large while the vehicleis moving, then the seating determination is deferred and an updateddetermination result cannot be obtained. Thus, for example, if apassenger boards the vehicle while it is stopped and does not sit fullyand stably in the seat until after the vehicle is moving, then eventhough the passenger is seated stably, the seating determination will bedeferred while the vehicle is moving and the vehicle vibration iscomparatively large. Consequently, there is a possibility that theapparatus will maintain the determination result of the previous cyclewithout obtaining an appropriate seating determination.

FIG. 7 illustrates the characteristic curves for a vehicle that isstopped while carrying an adult passenger (a 57-kg man). During a periodfrom a time t0 to a time t1, the vibration change amount is below thevibration threshold value TH/LαLow. Therefore, the seating determinationis executed. However, during a period from the time t1 to a time t2, thepassenger starts shaking his body or knees and causes a vehiclevibration to occur. The vibration change amount during this period ishigher than the vibration threshold value TH/LαLow and the seatingdetermination is deferred. During a period from the time t2 to a timet3, the vibration change amount is below the vibration threshold valueTH/LαLow and the vibration determination is executed. Then, during aperiod from the time t3 to a time t4, the passenger switches sides ofthe crossed legs and causes a large vehicle vibration to occur. Thevibration change amount during this period is higher than the vibrationthreshold value TH/LαLow and the seating determination is deferred.Afterwards, during a period from the time t4 to a time t6, the passengershakes his legs while keeping them crossed but the vehicle vibrationcaused is comparatively small. Thus, the vibration change amount isbelow the vibration threshold value TH/LαLow and the vibrationdetermination is executed. Since the difference between the vibrationthreshold value TH/LαLow and the vibration change amount is small, it isconceivable that there are times when the vibration change amountexceeds the vibration threshold value TH/LαLow depending on the way thepassenger shakes. Afterwards, during a period from the time t6 to a timet8, the passenger switches sides of the crossed legs again and causes alarge vehicle vibration to occur. The vibration change amount duringthis period is higher than the vibration threshold value TH/LαLow andthe seating determination is deferred. During a period from the time t8to a time t10, the vibration change amount temporarily falls below thevibration threshold value TH/LαLow and the seating determination isexecute. Then, during a period from the time t10 to a time t12, thepassenger's leg movement becomes rhythmical and a vehicle vibrationoccurs such that the vibration change amount exceeds the vibrationthreshold value TH/LαLow and the seating determination is deferred.

In this way, even if the vehicle is stopped and the vehicle vibration iscomparatively small, a posture or movement of a passenger can cause thevibration change amount to exceed the vibration threshold value TH/LαLowsuch that the seating determination is deferred. Consequently, there arefewer opportunities for the seating determination to be executed and aseating determination precision could decline.

Passenger Detection Operation when Vehicle is Moving

A vehicle passenger detection apparatus according to the illustratedembodiment, the vibration threshold value is set to a higher value whena fluctuation amount of the load detection signal is small than when afluctuation amount of the load detection signal is large. Consequently,as illustrated by the characteristic curves shown in FIG. 6 for a casein which an adult (49-kg woman) passenger is carried while the vehicleis moving, if the detected load is stable because the vehicle istraveling along a straight path, then at a time t1 the load changeamount will fall below the weight threshold value TH/Lβ at a time t1. Asa result, the apparatus will execute step S7 and step S8 of theflowchart shown in FIG. 5. At a time t2 when a state in which the loadchange amount is smaller than the weight threshold value TH/Lβ hascontinued for a prescribed amount of time, the apparatus proceeds fromstep S8 to step S9 and changes the vibration threshold value from thelower value TH/LαLow to the higher value TH/LαHigh. As a result, duringa period from the time t2 to a time t4, the vibration change amount isbelow the vibration threshold value TH/LαHigh and the seatingdetermination is executed even if the vehicle is moving.

At the time t4, the load change amount exceeds the weight thresholdvalue TH/Lβ and the apparatus proceeds from step S7 to step S10 of theflowchart shown in FIG. 5, thereby changing the vibration thresholdvalue from the higher value TH/LαHigh to the lower value TH/LαLow. Afterthe time t4 the vibration change amount exceeds the vibration thresholdvalue TH/LαLow and the seating determination is deferred such that theprevious determination result is maintained.

Later, the vehicle travels through a curve and a centrifugal forceacting on the seat 2 causes the detected load, i.e., the sum of the loaddetection signals (vibration waveform removed signals in thisembodiment) to decrease greatly in a case where the load detectionsignals are detected with two sensors. Meanwhile, the load change amountoutput is comparatively stable. At a time t5 the load change amountfalls below the weight threshold value TH/Lβ, and at a time t6 aprescribed amount of time has elapsed with the load change amountcontinuously below the weight threshold value TH/Lβ. Consequently, atthe time t6, the vibration threshold value is changed from TH/LαLow toTH/LαHigh. However, in the case shown in FIG. 6, the load change amountexceeds the weight threshold value TH/Lβ again at a time t7.Consequently, the vibration threshold value does not remain at the valueTH/LαHigh and is changed back to the value TH/LαLow such that theseating determination continues to be deferred.

In this way, when the load change amount is small and the detected loadoutput can be determined to be stable, the seating determination can beexecuted even though the vehicle is moving by increasing the vibrationthreshold value. As a result, more opportunities to execute the seatingdetermination can be obtained while the vehicle is moving.

Passenger Detection Operation when Vehicle is Stopped

As illustrated by the characteristic curves shown in FIG. 7 for a casein which an adult (57-kg man) passenger is carried while the vehicle isstopped, even if the passenger is shaking his body or knees, the loadchange amount is below the weight threshold value TH/Lβ during theperiod from the time t0 to the time t3. Therefore, the vibrationthreshold value is set to the comparatively high value TH/LαHigh and,since the vibration change amount does not fall below this vibrationthreshold valve TH/LαHigh, the seating determination is executed duringthe period from the time t0 to the time t3.

At the time t3, the passenger crosses his legs and the load changeamount exceeds the weight threshold value TH/Lβ. The apparatus proceedsfrom step S7 to step S10 of the flowchart shown in FIG. 5, therebychanging the vibration threshold value from the higher value TH/LαHighto the lower value TH/LαLow. As a result, the vibration change amountexceeds the vibration threshold value TH/LαLow and the seatingdetermination is deferred such that the previous determination result ismaintained.

Afterwards, at a time t4 the load change amount falls below the weightthreshold value TH/Lβ, and at a time t5 a prescribed amount of time haselapsed with the load change amount continuously below the weightthreshold value TH/Lβ. At the time t5, the vibration threshold value ischanged from TH/LαLow to TH/LαHigh. Although the passenger is shakinghis crossed legs, the seating determination is executed because thevibration change amount does not exceed the vibration threshold valueTH/LαHigh. Since the difference between the vibration threshold valueTH/LαHigh and the vibration change amount is large, it is unlikely thatthe vibration change amount will exceed the vibration threshold valueTH/LαHigh even if the passenger shakes somewhat strongly.

At a time t7, the passenger switches sides of the crossed legs and theload change amount exceeds the weight threshold value TH/Lβ, causing thevibration threshold value to be changed from TH/LαHigh to TH/LαLow. As aresult, the vibration change amount exceeds the vibration thresholdvalue TH/LαLow and the seating determination is deferred.

The passenger's leg movement becomes rhythmical and a vehicle vibrationoccurs, but the load change amount decreases and falls below the weightthreshold value TH/Lβ at a time t9. At a time t11, a prescribed amountof time has elapsed with the load change amount continuously below theweight threshold value TH/Lβ. Therefore, the vibration threshold valueis changed from TH/LαLow to TH/LαHigh. Since the vibration change amountis smaller than the vibration threshold value TH/LαHigh, the seatingdetermination is executed.

In short, the vibration threshold value is set to a higher value when afluctuation amount of the load detection signal is small than when afluctuation amount of the load detection signal is large. Thus, theseating determination is less likely to be deferred when a posture ormovement of a passenger causes a vehicle vibration to occur while thevehicle is stopped. As a result, more opportunities to execute theseating determination can be obtained when a passenger moves while thevehicle is stopped.

In the vehicle passenger detection apparatus 10 according to theillustrated embodiment, the vibration threshold value is set to a highervalue when a state in which the load change amount is below the weightthreshold value TH/Lβ has continued for a prescribed amount of time.Consequently, the vibration threshold value does not easily change whenthe load change amount fluctuates for a short period of time due to roadvibration or the like. As a result, the vibration threshold value usedas a reference when determining if a vehicle vibration is occurring canbe set in a more stable fashion.

Also, in the vehicle passenger detection apparatus 10 according to theillustrated embodiment, the vibration waveform removing section 14generates the vibration waveform removed signal, i.e., a load detectionsignal with a vibration waveform removed, from the load detectionsignals. The load change amount determination logic 15 then sets thevibration threshold values based on the vibration waveform removedsignals. The vibration change amount determination logic 16 determinesif a vehicle vibration is occurring based on a load detection signalthat has been converted to digital by the signal converting section 13.The passenger determination logic 17 a executes the seatingdetermination based on the vibration waveform removed signal.Consequently, the load change amount determination logic 15 and thepassenger determination logic 17 a can set the threshold valueaccurately and execute an accurate seating determination without beingaffected by the vibration waveform. The vibration change amountdetermination logic 16 can also execute an accurate vibrationdetermination by using a load detection signal that includes thevibration waveform. As a result, the precision of both the settings andthe determinations can be improved.

In the vehicle passenger detection section 10 according to theillustrated embodiment, the seat 2 (passenger seat 2 a) is supportedwith respect to the vehicle body 21 at a plurality of support points 24a to 24 d and the load sensors 11, i.e., a total of two load sensors 11a and 11 b, are provided at the two front and rear support points 24 aand 24 b located on the slide rail 22 located more toward the inwardside of the vehicle body 21. Thus, a cost reduction can be achievedbecause the number of expensive load sensors 11 is fewer than the totalnumber of support points 24 a to 24 d. Installing a number of loaddetection sensors 11 smaller than the total number of support points 24a to 24 d of the seat 2 is disadvantageous because the sum of the loaddetection signals is smaller than the load imposed by a passenger andbecause the apparatus is easily affected by the traveling state of thevehicle (e.g., rightward curve or leftward curve). However, when thevehicle vibration is large, the seating determination is deferred. As aresult, the determination precision of the passenger detection does notdecline due to reducing the number of load sensors 11 installed.

Effects that can be obtained with a vehicle passenger detectionapparatus 10 according to the illustrated embodiment are listed below.

(1) The vehicle passenger detection apparatus 10 comprises: loaddetecting part (load sensors) 11 a and 11 b that are installed in thevicinity of a seat (passenger seat) 2 a and detect a load acting on theseat 2 a; and a seat condition determining part (passenger detectionECU) 12 that determines a condition of the seat 2 a based on loaddetection signals from the load detecting part 11 a and 11 b. The seatcondition determining part 12 comprises: a vibration threshold valuesetting section (load change amount determination logic) 15 that sets avibration threshold value based on the load detection signals to serveas a reference when determining if a vehicle vibration is occurring; avibration determining section (vibration change amount determinationlogic) 16 that determines if a vehicle vibration is occurring based onthe load detection signals and the vibration threshold value; and a seatdetermining section 17 that executes a seating determination based onthe load detection signals when the vibration determining section 16 hasdetermined that a vehicle vibration is not occurring, and defersexecution of the seating determination based on the load detectionsignals and maintains a previous determination result when the vibrationdetermining section 16 determines that a vehicle vibration is occurring.The vibration threshold value setting section 15 sets the vibrationthreshold value to a higher value when a fluctuation amount of the loaddetection signal is small than when a fluctuation amount of the loaddetection signal is large.

As a result, deferments of the seating determination can be decreasedand opportunities for executing the seating determination can beincreased when the size of a vehicle vibration is used to decide whetherto execute or defer the seating determination.

(2) The vibration threshold value setting section (load change amountdetermination logic) 15 is configured to set the vibration thresholdvalue to a higher value when a state in which the fluctuation amount ofthe load detection signal is small has continued for a prescribed amountof time than when the fluctuation amount of the load detection signal islarge. As a result, the vibration threshold value serving as a referencefor determining if a vehicle vibration is occurring can be set in astable fashion even when the load change amount fluctuations for a shortamount of time due to road vibration or the like.

(3) The seat condition determining part (passenger detection ECU) 12 isprovided with a vibration waveform removing section 14 that removes avibration waveform indicating that a vibration is occurring from theload detection signals. The vibration threshold value setting section(load change amount determination logic) 15 finds a vibration thresholdvalue based on the vibration waveform removed signal obtained after thevibration waveform removing section 14 has removed the vibrationwaveform from the load detection signal, and the vibration determiningsection (vibration change amount determination logic) 16 determines if avehicle vibration is occurring based on the load detection signalsincluding the vibration waveform, i.e., the load detection signals asthey exist before the vibration waveform has been removed by thevibration waveform removing section 14. The seat determining section 17executes a seating determination based vibration waveform removedsignals, i.e., the load detection signals resulting after the vibrationwaveform has been removed by the vibration waveform removing section 14.As a result, the threshold value can be set, the seating determinationcan be executed, and the vibration determination can be executed basedon appropriate signals and the settings and determinations can beaccomplished with improved precision.

(4) The seat (passenger seat) 2 a is supported with respect to thevehicle body 21 at a plurality of support points 24 a to 24 d and a loaddetecting part (load sensor) 11 is installed with respect to at leastone of the support points (support points 24 a and 24 b) and notinstalled with respect to at least one of the support points. As aresult, cost reduction can be accomplished without lowering adetermination precision.

Although the present invention is explained herein based on theillustrated embodiment of a vehicle passenger detection apparatusaccording to the present invention, the invention is not limited to thisembodiment and includes any design changes, additions, or the like thatdo not depart from the scope of the invention as set forth in theclaims.

In the vehicle passenger detection apparatus 10 according to theillustrated embodiment, the passenger determination logic 17 a executesa seating determination regardless of the determination result obtainedby the vibration change amount determination logic 16 and decideswhether to update or to maintain the seat information based on thedetermination result obtained with the vibration change amountdetermination logic 16. However, the invention is not limited to such anapproach. For example, it is also acceptable to execute or defer theseating determination based on the determination result obtained withthe vibration change amount determination logic 16. Thus, when thevibration change amount determination logic 16 determines that thevehicle vibration is large, the passenger determination logic 17 a doesnot execute the seating determination. With this approach, number ofcomputations executed by the passenger determination logic 17 a can bereduced.

In the vehicle passenger detection apparatus 10 according to theillustrated embodiment, the weight threshold value (TH/Lβ) is a fixedvalue provided in the load change amount determination logic 15 inadvance. However, it is acceptable to change the value in response thepassenger who is sitting. For example, the weight threshold value couldbe set to 1(N) when an adult is sitting and 0.5(N) when a child issitting in a child seat. In this way, a more nuanced determination canbe accomplished.

Additionally, in the vehicle passenger detection apparatus 10 accordingto the illustrated embodiment, the vibration threshold value is set to ahigher value when a state in which the fluctuation amount of thevibration waveform removed signal is small has continued for aprescribed amount of time than when the fluctuation amount of thevibration waveform removed signal is large. However, it is alsoacceptable to set the vibration threshold value in accordance withchanges in the fluctuation amount of the load detection signal. Thus,the vibration threshold value is lowered immediately when the loaddetection signal falls below the weight threshold value and thevibration threshold value is raised immediately when the load detectionsignal is exceeds the weight threshold value. With this approach, too,deferments of the seating determination can be decreased andopportunities to execute the seating determination can be increased.

General Interpretation of Terms

In understanding the scope of the present invention, the term“comprising” and its derivatives, as used herein, are intended to beopen ended terms that specify the presence of the stated features,elements, components, groups, integers, and/or steps, but do not excludethe presence of other unstated features, elements, components, groups,integers and/or steps. The foregoing also applies to words havingsimilar meanings such as the terms, “including”, “having” and theirderivatives. Also, the terms “part,” “section,” “portion,” “member” or“element” when used in the singular can have the dual meaning of asingle part or a plurality of parts. Finally, terms of degree such as“substantially”, “about” and “approximately” as used herein mean areasonable amount of deviation of the modified term such that the endresult is not significantly changed. For example, these terms can beconstrued as including a deviation of at least ±5% of the modified termif this deviation would not negate the meaning of the word it modifies.

While only selected embodiments have been chosen to illustrate thepresent invention, it will be apparent to those skilled in the art fromthis disclosure that various changes and modifications can be madeherein without departing from the scope of the invention as defined inthe appended claims. Furthermore, the foregoing descriptions of theembodiments according to the present invention are provided forillustration only, and not for the purpose of limiting the invention asdefined by the appended claims and their equivalents.

1. A vehicle passenger detection apparatus comprising: a load detectingpart installed in the vicinity of a seat of a vehicle to detect a loadacting on the seat; and a seat condition determining part configured todetermine a condition of the seat based on a load detection signal fromthe load detecting part, the seat condition determining part including avibration threshold value setting section configured to set a vibrationthreshold value based on the load detection signal such that thevibration threshold value is higher when a fluctuation amount of theload detection signal is small than when the fluctuation amount of theload detection signal is large, a vibration determining sectionconfigured to determine if the vehicle vibration is occurring based onthe load detection signal and the vibration threshold value, and a seatdetermining section configured to execute a seating determination basedon the load detection signal when the vibration determining sectiondetermines that the vehicle vibration is not occurring, and to deferexecution of the seating determination to maintain a previous seatingdetermination result when the vibration determining section determinesthat the vehicle vibration is occurring.
 2. The vehicle passengerdetection apparatus recited in claim 1, wherein the vibration thresholdvalue setting section is configured to set the vibration threshold valuesuch that the vibration threshold value is higher when a state in whichthe fluctuation amount of the load detection signal is small hascontinued for a prescribed amount of time than when the fluctuationamount of the load detection signal is large.
 3. The vehicle passengerdetection apparatus recited in claim 1, wherein the seat conditiondetermining part includes a vibration waveform removing sectionconfigured to remove a vibration waveform indicative of a vibration fromthe load detection signal, the vibration threshold value setting sectionis configured to determine the vibration threshold value based on avibration waveform removed signal resulting after the vibration waveformremoving section has removed the vibration waveform from the loaddetection signal, the vibration determining section is configured todetermine if the vehicle vibration is occurring based on the loaddetection signal before the vibration waveform is removed, and the seatdetermining section is configured to execute the seating determinationbased on the vibration waveform removed signal.
 4. The vehicle passengerdetection apparatus recited in claim 1, wherein the load detecting partis installed with respect to at least one of a plurality of supportpoints, at which the seat is supported with respect to a vehicle body,and not installed with respect to at least one of the support points. 5.The vehicle passenger detection apparatus recited in claim 4, whereinthe load detecting part is installed with respect to at least two of thesupport points.